HUE027766T2

HUE027766T2 - Carbon brush for transferring high currents

Info

Publication number: HUE027766T2
Application number: HUE09174288A
Authority: HU
Inventors: Henrik Neuweger; Hans Lippert; Thomas Weber; Andreas Reetz
Original assignee: Schunk Kohlenstofftechnik Gmbh
Priority date: 2008-11-28
Filing date: 2009-10-28
Publication date: 2016-10-28
Also published as: US20100133951A1; DK2192660T3; CN101783473A; DE102008059478B4; EP2192660B1; AU2009233633A1; DE102008059478A1; US8847463B2; EP2192660A2; AU2009233633B2; ES2568500T3; EP2192660A3

Description

C&RBOfé BF OS M IFOR T HAP S M IT TING HIGH CURRENTS

The present invention relates to a carbon brush for transmitting high current?*, having a connecting element for connecting an electrical conductor and a consumable contact element with a contact surface that is designed to contact a slip ring device, particularly a commuta tor,

Carbon brushes of the kind described in the introduction ate often referred to as "industrial carbon brushes" and are used particularly in situations that require transmission of high currents, often in excess of 20 a spare/cur. In this context,, carbon, brushes of such kind are need in motors and generators, and use of the generators mich these carbon brushes is becoming increasingly popular in wind turbines.

Because of the high outputs the industrial carbon brushes are required to transmit in such cases, it is imperative to add sufficient fractions of metallic inclusions to the carbon, to help to reduce contact resistances as much as possible and so minimise the heating of the carbon brushes caused by electrical reel stance. To this end it has proven advantageous to manufacture the carbon brushes, which are usually produced as molded parts, from a par.ticui.ate molding compound consisting mostly of a suitable metal, particularly silver, In practice, the silver content in industrial carbon brushes is frequently as high as 60% and more, Is a result, the production costs for carbon brushes are considerable due to the quantity of silver alone, without taking into account the production costs associated with any given process.

The known industrial carbon brushes are manufactured as essentially homogeneous molded parts, the composition of which is consistent for both the contact element that contacts the slip ring device during operation and the connecting elemen: to which the electrical connecting conductor is connected. Consequently, this neons that a significant portion of the silver in the carbon brush* which is consumed together with the carbon in the cor,tact element as the carbon brush is worn dóén, ie also present in the connecting element, where the specific material .properties· of the silver are not required, even though they are essential for interacting with the carbon in the contact clonenr, The connecting element in the carbon brush serves instead to establish an electrically conductive connection with the connecting conductor. Once the contact element has been used up, the connecting element is usually disposed of, together with the silver it contains.

Document ö'S-ä~5411S83 teaches that the material composition of the contact element consists of two graphite powders and a hinder.

Accordingly, the methods used until non for manufacturing industrial carbon crushes have entailed using a quantity of silver, not all of which is needed for operating the carbon brushes.

The object of one present invention is therefore to suggest a carbon brush for transmitting high currents which enables the carbon brush to function reliably and at the same time is associated with lower manufacturing costs than the known carbon brushes.

This object is solved with a carbon brush having the features of claim 1.,

The carbon brush according to the invention for transmitting high currents includes a molded body the composition of which is varies according to the different functions of the brush areas, in which the connecting element serves to provide a connection with an elect, rice 1 conductor and the contact element serves to ensure uninterrupted contact with the material of the counter-contact element or the slip ring device, and unlike the connecting element most ensure flush contact with the material of the counter-contact through near, in the carbon brush according to the invent 1 on, the connecting element and the contact element merge in a layer transition zone aligned: perpendicularly to the direction of near of the carbon: brush and form a one-piece molded body having different compositions that are adapted to the different functions of the connecting element and the contact element. Accordingly, the carbon fraction in the contact element is greater than the carbon fraction in the connecting element, because the carbon i.s important for creating the desired low-friction contact. Besides its carbon content, the contact element also includes a metal fraction, which is different from the metal fraction in the connecting element, so that the metal fractions in each may he optimized for the different functions of the metal fractions in the contact element and the connecting element. Thus, a metal may be selected for the contact element that both enables generation of a desirable low contact resistance, and also has relatively low abrasive properties so as to minimize its negative effect on the advantageous properties of the carbon for the purposes of establishing a low-friction contact. For the connecting element, which is separated from the consumable part of the carbon brush by the layer transition zone, and for which wear-related properties are therefore of secondary importance, a metal, fraction may thus be used that has both sufficient mechanical strength to fulfil its mechanical connecting function and good electrical conductivity for creating the electrical connection with the connecting conductor, without regard tor its abrasive properties.

The carbon brush according to the invention is thus defined as a carbon brush in which areas are separated by the layer transition, zone, each of which areas cay be optimized with respect to their essentia.! functions independently of the other area. In this way, it is ai so possible to significantly reduce the proportion of silver in the carbon brush according to the rnvenri.cn compares with the known carbon brush because the silver content is then only need for the contact elector. Accordingly, in a corresponding embodiment of the carbon brush according to the invention., the remaining part of the brush, 'which oust be disposed of and essentially consists only of the connecting element when a carbon brush has beer: worn door· to the layer transition, tőrre, contains no silver at ail.

In a preferred embodiment of the carbon brush according to the invention,· the contact element has a metal content composed costly of silver and the connecting element has a metal, content composed mostly of copper. In this way, it is possible to create a carbon brush that is optimized with regard to selecting the respective metal for the contact element and the connecting element.

The fraction of metal in the contact element may be 50% or mere depending on the requirement for the carbon brush. Depending on. this requirement, the metal content in. the contact element may be up to 100% of a copper material or a copper alloy. •A particularly high-strength embodiment* capable of withstanding extremely high mechanical loads, is created if the connecting element is made from 100I copper or a copper alloy.

If, as In a .particularly advantageous embodiment of the carbon brush, the contact element nett to the layer transition äone has an indicator area formed with a different composition than a consumable area and provided with a contact surface, it is possible to form a consumable or maintenance indicator on the carbon brush as a multilayer construction is worn down without the need to provide special, separate: contact devices. In this embodiment, it is simple to exploit the advantageous effect that is created when the contact surface is formed in the indicator area, causing the resistance to change because the metal content of the indicator area differs from that of the consumable area, this change in resistance may be used as a signal to indicate that the carbon brush needs to be replaced.

Regardless of the formation of an indicator area on the carbon brush, In any case it is advantageous if the connecting element has a fiat connecting surface tor creating a soldered or welded connection to the electrical conductor, so that it is possible to create a simple* fiat attachment to the connecting conductor with a soldered or welded connection without the need for special retaining devices on the connecting element, in the following, preferred embodiments of the invention will be explained with reference to the drawing.

In the -drawing:

Fig, 1 shows a first embosom ru. of a carbon brush;

Fig. 2 shows the carbon brush of Fig·. 1 with a connection side conformed on the connecting element of the carbon brush;

Fig, 3 shows a further embodiment of a carbon brush;

Figs, 4a. to 4c show a method for man « £ act u r i nq the carbon brush of Fig. 1.

Fig, 1 shows a carbon brush 10 having a contact element 11 and a connecting element 12, each of which are manufactured from: individual molding particle® 24, 25, 26 (Fig® 4a.; and. are connected to each other in a single part via a laver transition rone 13. The carbon brush shown in Fig. 1 may be produced by means of the compression molding method illustrated in the following with reference to Figs- 4 a to 4« in such manner that carbon brush 10 i.s created as a molded part by suitable compression, and the or assure erected on the mold particles of contact elements IX and 12 causes connecting element 12 to permeate contact element 11 in the layer transition zone 13, this permeation being limited to layer transition zone 13-

In the case of the embodiment shown in Fig. 1, contact element II consists of a mixture of 60 percent by weight silver and 40 percent by weight carbon and is consumed in the direction of the compression force indicated in Fig- ! by the arrow. In the ease of the embodiment of carbon brush 10 shown in Fig. 1, connecting element 12 is made of pure copper.

Contact element 11 has a contact area 16 adjacent with a contact surface If of a. commutator ring 13 indicated in

Fig. 1, which contact area is conformed to lie flush with the contour of contact surface 14.

Fig. 2 shows a flat connecting surface 17, formed in the present case by the rear face of connecting element 12, and which serves to create an electrically conductive connection between connecting element 12 and electrical connecting conductor 19, created here for example by a soldered connection IS,

Fig. 3 shows a farther embodiment of a carbon brach 2Q, differing from the carbon brush 10 shown in Fig, 1 in that it has a contact element 21 that has a consumable area 22 adjacent contact surface lb and an indicator area 23 attached to the consumable area and located adjacent layer transition cone 13, Similarly to the carbon brush 10 shown in Fig. X, a connecting element 12 is attached to layer transition sons 13,

In the embodiment of the carbon brush 20 shown in Fig, 3, indicator area 23 is distinguished from consumable area 22 by a relatively lower silver content.

As is shown in Figs, 4 a to 4 c., one option for manufacturing carbon brush 10 consists in using a molding device 27 including a molding tool 28 and a number of form punches 29 to 31,. wherein in a first step separate mold areas 33 and 34. are filled with mold particles 24, 25 and 26 corresponding to the: desired material compositions of contact element 11 and connecting element 12 are filled, for example by a slide. In the example of carbon brush 10, mold particles 24: are graphite; mold particles 25 are silver and mold particles 26 are copper.

Therm slide 32 is withdrawn from the molding tool (Fig,. 4b) so that mold particles 24; 25 disposed in first mold area 33 come into direct contact with mold particles: 26 located in second mold area 34, and layer transition sene: 13 is formed. When mold particles 21 ; 25 and 26 are compressed subsequently, carbon brush 10 is finally produced by form punch 31 which is lowered from above (Fig. 4e). Subsequent partitioning, as illustrated by carbon brush 20 in Fig. 3; may be performed with a corresponding number and arrangement of additional slides in the molding tool.

ABSTRACT

The invention, relates to a carbon brush (10, 20} for. tréneri ::. zing high currents, comprising a connecting element {.12) for connecting an electric ai connecting conductor (19} and a consarable contact element (11) having a contact surface (16} that la designed to lie flush against a commntatox device:, wherein the connecting element and the contact element merge in a layer transition zone (13) aligned perpendicularly' to the direction of near of the carbon brush and form a one-piece molded body, wherein the connecting element and the contact element, nave different compositions,, such that a carbon content of the contact element is greater than the carbon content of the connecting element and the contact element and the connecting element have metal contents, the contact element having a metal content differing from that, of the connecting element, ( F ** '7 s 1

Claims

COFFEE FOR BACKGROUND COST TRANSFER SAB Da Imi I g i y p on to R

A carbon brush (10, 20) for transmitting a high current with a connecting portion (12) to be connected to a carbon brush electric wire (19) and a wear contact part (11} having an engaging surface (1 €; a connector part and a contact portion) of the connector). In the direction of the carbon brush wear direction, the layer passes through each other in a zone (13) and forms a body formed in one piece, the connecting part and the contact part are of different material composition, such that the carbon content of the contact part is greater than the carbon content of the coupling part, and the contact portion is a contact material. and the connector part comprises a metal component and a metallic component other than the connector portion in the touch portion.

The carbon brush according to claim 1, characterized in that the tongue gap (XI; comprises a metal component consisting mainly of ezine, and the connecting part (.12) comprises a metal component which is largely made of copper.

A carbon brush according to claim 2, characterized in that the contact part (II) is made of at least 50 sheets of silver or silver alloy and at least 50 strips of copper or copper strips of the connecting part (.12) are in the form of a sealing element. Carbon brush according to claim 3, characterized in that the connecting part (12) is made up of 100% fcc of copper or copper alloy. а. The carbon brush according to one of the preceding claims, characterized in that the contact part (1.1) is adjacent to the layer A (13) adjacent to the layer (13) with the contact surface (16?) And the other parts (23) having a different composition (23). A carbon brush according to any one of the preceding claims, characterized in that the connecting part (12) has a flat connection surface (13) for forming a soldered or welded bond. with the electric wire, (19)